The present invention relates to cutting parts from a patterned sheet material, and more particularly, to transforming part peripheries or markers prior to cutting, in response to a distance between a pattern characteristic projected on the sheet material at an estimated location and a corresponding actual location on the patterned sheet material.
Upholstered furniture is generally covered with leather, vinyl or fabric. A significant part of the manufacturing cost of furniture is associated with cutting the fabric. Therefore, most inexpensive furniture is covered with vinyl, plain fabric, or fabric with a small overall pattern. When plain fabric, fabric with a small overall pattern or vinyl is used, it can be cut by placing one layer on top of another, building a stack that is then cut in a single process. For this kind of production, automatic machines are known that can stack the sheet material and then cut the stack in the required pattern pieces with a computer guided cutter.
More expensive furniture uses fabric that must be matched when applied. Examples of matching are (1) a pattern characteristic that xe2x80x9cextendsxe2x80x9d across multiple components of a piece of furniture, such as a stripe that starts at the lower back of a sofa and continues up the back, over the top and down the seat back, across the seat and down the front to the bottom; (2) a particular pattern characteristic having a predetermined location on the finished product, such as each cushion having a particular flower centered thereon; or (3) a single pattern characteristic that is retained by adjacent furniture components, such as trees or animals that are larger than single piece of fabric in the furniture and which must appear to flow in an uninterrupted manner across two or more pieces.
Matched fabric is typically manufactured by weaving, knitting or printing. The manufacturing process usually includes passing the fabric over many rollers. As a result of the manufacturing process, the fabric typically has a skew (the filler or yarn going from one edge to the other across the web is not perpendicular to the length of the fabric), or bow (the filler yarn is not straight), or both. Moreover, the fabric is typically printed with a printing cylinder or by screen printing. With either method, the repeat of the pattern is not necessarily constant. Even if the repeat was originally perfect, the fabric may stretch as it is processed, thereby introducing error.
Accordingly, the manufactured fabric typically differs considerably from an xe2x80x9cidealxe2x80x9d in terms of skew, bow and repeat.
The fabric may also have defects including, but not limited to dropped threads, holes and printing defects. Because of these many defects, patterned fabric cannot be stacked with any reliability of pattern match and must therefore be cut one layer at a time.
The most common method for matching and cutting patterned fabric includes spreading the fabric on a cutting table. A highly trained operator places or nests the individual templates of the pattern on the fabric in the appropriate places so that after cutting, sewing and upholstering the furniture, the pattern on the furniture matches in the desired configuration. After the individual templates of the pattern are in their proper place, the operator marks with chalk around each template. The pattern templates are then removed and the fabric is cut with a rotary knife or scissors.
Alternatively, an initial nest is generated by a computer program. The program can automatically position pattern pieces within a digital periphery of the fabric, or accept a manual override. Traditionally, the computer applies the nesting program to an ideal fabric pattern. In recent developments, an actual pattern of the fabric is scanned into the computer. The scanned fabric and template peripheries are then displayed on a monitor for rotation and/or translation by an operator.
After nesting is complete, the data is used to guide an automated cutting machine. Even with a scanned fabric pattern and computer generated nesting, the cutting machine instructions include moving the cutting knife to the center of the fabric pattern for each major nested group, where a stop instruction is implemented to stop the cutting machine. Once stopped, the operator can align the cutter with a particular location on the fabric pattern. That is, the operator can move the cutting machine by using a joy stick or jog buttons so that the pattern nest coincides with the actual pattern on the fabric.
U.S. Pat. No. 3,805,650 discloses the use of subprograms for individual pieces to be positionally correlated with the designs, wherein a plastic template with an index mark is manually positioned on the fabric. The index marks on the plastic template are then aligned with a pointer on the cutting head to completely identify the position of the templates by providing both location and orientation of the templates and corresponding pieces.
U.S. Pat. No. 5,172,326 discloses the use of a video camera for capturing the image of a printed fabric and displaying the captured image on a computer screen. Pattern templates are called from a memory and superimposed upon the captured pattern piece on the screen. A customized template pattern is then formed by reorientation of the pieces, and the resulting cutting instructions are forwarded to an automated cutter.
U.S. Pat. No. 4,739,487 discloses storing image coordinates of a pattern in a computer. The stored image coordinates are used to form an image and the image is projected onto the material. The operator may translate or rotate the projected image to achieve a preferred arrangement on the material.
U.S. Pat. No. 4,941,183 discloses a method of optimizing the pieces of material to be cut from a sheet including preparing a reduced scale template corresponding to the shapes of pieces to be cut; placing the templates on a projection device and projecting the images of the templates onto the material; manually positioning the templates to optimize the position of the templates; generating a digital template representation and cutting the material.
The prior art systems that are relatively inexpensive address only a specific flaw type in a pattern. Alternatively, those systems that address multiple flaws such as skew and bow require extensive image capturing equipment and are hence prohibitively expensive. Further, while the prior art systems employing scanners for acquiring an image of the patterned fabric reduce human intervention, the scanners currently have limited resolutions and may fail to identify minor flaws in the pattern. In addition, the scanners require relatively sophisticated calibration to obtain their maximum efficiency.
Therefore, the need exists for a system of adjusting a nested or individual template with respect to any of a variety of flaws on a piece of patterned sheet material. The further need exists for employing operator input to identify and adjust an estimated point projected on the sheet material to accommodate a flaw in the patterned fabric, thereby forming a distorted or shifted part periphery or template corresponding to the actual pattern on the fabric.
The present invention includes a method and apparatus for adjusting a marker or a part periphery with respect to a patterned sheet material to accommodate flaws in the sheet material such as varying repeat, bow and skew.
Generally, the present invention includes selecting a given pattern characteristic of a patterned sheet material; projecting a reference image at an estimated position on the sheet material; identifying an actual corresponding pattern characteristic and modifying the estimated position in response to a difference between the estimated position and the actual corresponding pattern characteristic. The modification of the estimated position includes a transformation of the estimated pattern characteristics in response to the identified actual pattern characteristic, thereby reducing the need to scan an entire segment of the fabric or identify and input every pattern characteristic with a given segment. The calculated difference between the ideal fabric pattern and the estimated fabric pattern is used to transform the parts to be cut from the sheet material, wherein the parts may be proximal to or spaced apart from the portion of the sheet material in which the actual corresponding pattern characteristic resides. The transformation may include a translation, rotation, distortion or any combination. As used herein, distortion includes a manipulation that changes the relative position of two locations of a part periphery. A distortion of a part periphery includes a change in the relative position of the constituent line segments. Translation and rotation retain the relative position of all the constituent line segments in a part periphery, and are therefore not a distorting manipulation.
Specifically, the present invention encompasses shifting a part periphery in response to a distance between an estimated and actual repeat frequency in the fabric, and transforming an estimated pattern or part periphery in response to an actual deviation of the patterned sheet material from an ideal pattern. The identification and inputting of the actual pattern characteristics includes projecting an estimated pattern characteristic position or part periphery upon the actual fabric. The process of projecting an estimated pattern characteristic position and adjusting its location to an actual pattern characteristic location can be implemented at spaced apart locations on the sheet material, wherein an interpolation process is applied to the intermediate area of the sheet material. Similarly, the projecting and adjusting can be implemented at adjacent locations on the sheet material and an extrapolative process is used to determine the pattern characteristics spaced from the projected area. Further, a combination of techniques may be employed depending upon the particular pattern characteristic.